Summary of Workshop on Fate of Pharmaceuticals in the Environment
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Klaus Kümmerer University of Freiburg, Germany Virginia L. Cunningham GlaxoSmithKline, USA
Correspondence Address Dr. Klaus Kümmerer, Head Applied Environmental Research Section, Institute of Environmental Medicine and Hospital Epidemiology, Breisacherstraße 115 B, D-79106 Freiburg, Germany (e-mail: Klaus.Kuemmerer@ uniklinik-freiburg.de).
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Summary of Workshop on Fate of Pharmaceuticals in the Environment
THE ISSUE Pharmaceutical compounds, as a class, generally possess characteristics that make them different from conventional industrial chemicals for which standardized environmental fate and transport testing protocols were developed. They have comparatively large, chemically complex molecular structures and are generally ionizable, with multiple ionization sites spread throughout the molecule. In addition, human pharmaceuticals are introduced into the environment from use by patients and may be transformed by various human metabolic processes before excretion. These characteristics need to be kept in mind when establishing the environmental form to be evaluated (parent, metabolites, other), designing fate and effects testing strategies, interpreting test results, predicting environmental fate, and carrying out environmental risk assessments. In particular, because most pharmaceuticals are charged and hydrophilic, the sorption of these compounds to particles in municipal wastewater treatment plants, surface waters, and sediments cannot be predicted from parameters that are often used for predicting partitioning of hydrophobic compounds, such as the octanol/water partition coefficient.
WORKSHOP CONCLUSIONS Critical issues to be considered as part of the environmental risk assessment of pharmaceuticals include 1. Chemical, physical, and pharmacological characteristics of the compounds expected to enter the environment (parent, metabolites, degradation products, etc). Adsorption, distribution, metabolism, and excretion (ADME) data from animal and human tests may serve as useful guidance. This information is also important in estimating quantities of various species entering the environment. 2. Release scenarios, including direct discharges and discharges after wastewater treatment from patient use, spills from transport, disposal of unused medicines in landfills. 3. Appropriateness of predictive models such as structure-activity or structure-property relationships (ensure that models were developed using data sets representative of compounds under consideration). Models developed using neutral, hydrophobic chemical data sets may not be applicable to large, ionic, polar, hydrophilic (relatively) chemicals such as pharmaceuticals. 4. Appropriateness of fate and effects testing strategies. For direct discharge scenarios, ready biodegradability is most applicable; for discharge after secondary wastewater treatment, biodegradability under simulated secondary wastewater treatment conditions may be preferred. Consider adding metabolite testing if metabolism is signifi-
Drug Information Journal, Vol. 41, pp. 193–19
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